TENS of thousands of diabetics are potentially being exposed to a bad batch of insulin as authorities quietly investigate serious concerns raised by a Miami mother.

The Therapeutic Goods Administration (TGA) has chosen not to issue an alert about NovoRapid Penfill despite dozens of patients and families linking it to "shocking" changes in blood glucose control, the Gold Coast Bulletin reports.

With a batch of 25 vials lasting up to three months, parents have reported children being hospitalised with dangerously high sugar levels, with others crashing to prolonged lows.

Selena Tranter, whose daughter has Type 1 diabetes, has spent the past week urging the TGA and pharmaceutical company Novo Nordisk to warn diabetics of the possible need to change insulin batches after finding a solution to her own "two months of torture".